As electric insulating oils for electric instruments such as transformers and capacitors, those consisting of mineral oils containing polychlorinated biphenyls (referred to hereinafter as “PCBs”) excellent in electrical insulation properties were generally used. However, the toxicity of PCBs to the living body has been confirmed, so that in Japan, the production and import of PCBs have already been prohibited, and use of electric insulating oils containing PCBs came to be substantially prohibited. PCBs-containing electric insulating oils and the like used in the past might cause environmental pollution during their disposal process and have thus been stored as they are until now for a long time by manufacturers of electric instruments, enterprises using such oils, and industrial waste disposers.
Meanwhile, with the background of establishment of safe chemical decomposition methods of PCBs, the PCB Special Measures Law was enacted in 2001 in Japan, and this law required that all PCBs wastes including PCBs-containing electric insulating oils which had been used or stored, be disposed of by July, 2016.
It was initially assumed that PCBs wastes that should be disposed of under the PCB Special Measures Law were limited to those electric insulating oils and the like which had been manufactured or used until production and use of PCBs were prohibited and which had been stored heretofore. However, there were cases where PCBs estimated to be mixed during the production process were detected in electric insulating oils and the like manufactured after prohibition of use of PCBs, and thus some electric insulating oils used at present in electric instruments such as transformers may correspond to PCBs wastes subject to the PCB Special Measures Law. The PCB Special Measures Law set out the time limit as described above, so there has been demand for promptly judging whether electric insulating oils used in existing electric instruments and the like correspond to the PCBs wastes subject to the PCB Special Measures Law (that is, oils and the like containing PCBs at a concentration of not less than 0.5 mg/kg correspond to the PCBs wastes subject to the PCB Special Measures Law, and judgment of whether oils and the like correspond to the PCBs wastes or not is referred to as PCB screening).
Whether samples collected from objects such as electric insulating oils contain PCBs at a predetermined concentration is judged usually on the basis of analysis results by highly sensitive analyzers such as gas chromatography-mass spectrometry (GC-MS) and gas chromatography-electron capture detection (GC/ECD), for which the samples should be subjected to advanced pretreatment to remove interfering components which can affect analysis results. Such pretreatment is carried out in accordance with the method described in Appendix No. 2 in Announcement No. 192 issued in 1992 by the Ministry of Health and Welfare of Japan “Method of Testing Standards Concerned with General Waste Subject to Special Control and Industrial Waste Subject to Special Control” (referred to hereinafter as an “official method”). However, the official method requires many steps of complicated treatments such as dimethylsulfoxide (DMSO)/hexane partition, sulfuric acid treatment, alkali treatment and silica gel column treatment, thus requiring a long time by day until completion and costing very high to be performed.
However, it is estimated that about 6 million electric instruments such as transformers are in use in Japan, so that when all electric insulating oils in these electric instruments are to be pretreated and analyzed by the official method, huge amounts of time and cost are required. Accordingly, it is substantially difficult under present circumstances to subject electric insulating oils in all electric instruments to PCB screening until the time limit stipulated under the PCB Special Measures Law.
Accordingly, a method for pretreating the objects has been examined as a substitute for the official method. For example, JP 2003-114222 A (particularly, paragraph numbers 0004 and 0007) describes a pretreatment method in accordance with the method stipulated in JIS K 0311 “Method for Determination of Dioxins in Stationary Source Emissions”. In this pretreatment method, organic components in a sample collected from an object to be judged are extracted with an organic solvent to prepare an extract, and this extract is passed through a silica gel column and an alumina column in this order in chromatography. On this occasion, part of impurity components other than PCBs contained in the extract is decomposed during passage through the silica gel column, and the resultant decomposition product is captured by the silica gel column. Then, when a developing solvent passed through the alumina column is collected, a solution of PCBs (that is, a solution of PCBs in the developing solvent) from which impurity components are removed is obtained, and this solution can be used as an analytical sample.
However, the substitute method described above is troublesome in preparing an extract from a sample of an object to be judged, the time necessary for treatment still remains so long as about 2 to 3 days, and the cost for pretreatment is high. Accordingly, the substitute method is substantially meaningless at least as a pretreatment method for PCB screening, which is substituted for the official method.
An object of the present invention is to enable PCBs to be extracted by an easy operation in a shorter time from an oily liquid such as an electric insulating oil containing PCBs.